The present invention relates to the field of machine recognition of magnetically printed characters on a document, and more particularly to a document reader system in which a multiple-gap magnetic read head is used in reading magnetized characters embodied in the form of E-13B character font printed on a document.
In single-gap magnetic character reading systems, a single analog input waveform is obtained by passing the characters to be sensed, normally printed on a document, beneath a magnetic read head at least as wide as the height of the characters and having a single flux gap. The signal generated by the read head is a derivative waveform representing the rate of change of magnetic flux transversing the head as the characters are scanned. Since the distrubution of ink, and thus flux, associated with each different character is unique, the waveform derived for each different character uniquely identifies that character.
In order to increase the amount of information that can be obtained when scanning the magnetically imprinted characters, multiple-gap magnetic read heads have been proposed in which multiple waveforms are produced. Whereas the single-gap read head produces an analog waveform as a result of the D.C. magnetization of the channels to be read, the multiple-gap read head produces a magnetic image of the character as a result of the A.C. magnetization of the character. Problems found in using a single-gap read head lie in determining from the information generated the start of the character wherein ink particles are encountered adjacent the character due to poor printing conditions. Also, the pigments of the magnetic ink used in the printing operation may not have been uniformly dispersed throughout the character, which produces information not capable of being used in the recognition process. It is therefore an object of this invention to provide an improved character recognition system. It is another object of this invention to provide a character recognition system which minimizes the effect of ink splatter in determining the start of the characters to be read. It is another object of this invention to utilize the maximum amount of information found in the waveforms generated by the character that is read.